Electric compressor having magnets disposed in magnet slots of rotor core

ABSTRACT

In a method for assembling an electric compressor which contains a rotor having built-in magnets, magnets in a pre-magnetization state are inserted into a plurality of slots of a magnetizing jib made with a nonmagnetic material. After magnetizing the magnets, the magnetizing jib is fitted to the rotor to have the magnets transferred into magnet slots. A magnetizing method and an assembly method for implementing high reliability electric compressors at low manufacturing cost is implemented

This application is a divisional application of application Ser. No.10/515,600, which is a U.S. National Phase Application of InternationalApplication PCT/JP2004/002069, filed Feb. 23, 2004.

TECHNICAL FIELD

The present invention relates to a magnetizing jig for magnetizingmagnets to be inserted in a rotor of an electric compressor, and amagnetizing method using the jig. The present invention relates also tomethods for assembling rotors and electric compressors using themagnetizing jig and the magnetizing method.

BACKGROUND ART

In the growing concern with environmental conservation, theenergy-saving activities are being accelerated also in the industrialfields of home-use refrigerators and air conditioners. In the sector ofelectric compressors for compressing the refrigerant gas, an increasingnumber of motors employ such a rotor provided with magnets builttherein. A conventional method of magnetizing the magnets is disclosedin Japanese Patent Laid-Open Application No. 2002-300762. According tothe method disclosed in the patent, the magnets built within a rotor aremagnetized by an electric current delivered to the stator's coil.

In the following, the above conventional magnetizing method is describedreferring to FIG. 11 and FIG. 12. FIG. 11 shows a sealed vessel of aconventional electric compressor (hereinafter referred to as acompressor), sectioned vertically. FIG. 12 shows the conventionalcompressor, as viewed from the above, whose sealed vessel has been cutinto two pieces. Sealed vessel 1 houses motor 5 and rolling-piston typecompressing element 10 driven by motor 5. Motor 5 includes rotor 8having built-in magnets 7 a pre-magnetization state and stator 9 whichis fixed an to inner surface of the sealed vessel. Compressing element10's shaft 11 is coupled and fixed with rotor 8. Coil 13 of stator 9 isreinforced and fixed with an immersing varnish.

A method of magnetization in the above-configured compressor isdescribed below.

Shaft 11 is fixed fastened at a certain specific position with no rotarymotion allowed, and then a certain specific electric current isdelivered to coil 13 of the stator. Magnets 7 at the pre-magnetizationstate are magnetized by the magnetic fields thus generated. This hasbeen one of the generally-used methods for magnetizing the magnets builtin a rotor.

However, in a case where a neodymium magnet or the like rare earthmagnet is used for the magnet, it requires such magnetic fields severaltimes as strong as compared with conventional examples where a ferritemagnet is used for the magnets.

Strength of magnetic fields is in proportion to the strength of electriccurrent. So, it requires a large electric current to generate strongmagnetic fields.

For generating a large current used for the magnetization, the electricenergy is once stored in a capacitor, and then dischargedinstantaneously. At this moment of electric discharge, the coil woundaround a stator is heated by the large current and at the same timeill-affected by the strong magnetic fields. As the result, the coil isliable to be deformed, or seriously damaged.

In the case of synchronous motors, among other motor types, where therotor is provided with a secondary conductor disposed at thecircumference of the rotor's iron core portion, the magnetizing effectsare retarded by the secondary conductor. As the result, it requires anelectric energy of higher strength for the magnetization. This meansthat the conventional magnetizing method which makes use of an electriccurrent delivered to a coil causes a substantial damage on the coil.Eventually, it will make it very difficult to use the magnetizing methodin normal production. In order to prevent the damage the stator's coilcan be immersed in a varnish, in order to have the coil physicallyreinforced and fixed. However, immersing a coil in a varnish accompaniesa substantial increase in the number of process steps, resulting in anincreased cost. Meanwhile, a magnetized magnet can be inserted in arotor if its magnetic force is moderate; but it may not be easy toinsert a neodymium or the like rare-earth magnets, which have farstronger magnetic force, after they are magnetized. Such magnets readilystick onto the rotor's core iron and significantly deteriorate theefficiency of operation.

The present invention addresses the above problems, and aims to offerreliable compressors at lower cost. A magnetizing jig and a method formagnetization serving the above objective are also disclosed.

DISCLOSURE OF THE INVENTION

The present invention offers a magnetizing jig made of a nonmagneticmaterial provided with a plurality of slots for retaining magnet.

Also offered by the present invention is a method for assembling arotor, which method includes a step of inserting the magnet at apre-magnetization stage into the magnetizing jig which is made of anonmagnetic material and provided with a plurality of slots, a step ofmagnetizing the magnet by delivering electricity to a coil disposedaround the outer circumference of the magnetizing jig, a step of fittingthe magnetizing jig to the rotor at an end-face, and a step of pushing amagnetized magnet out of the jig's slot and inserting it into a magnetslot.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top plan view of a magnetizing jig in accordance with afirst exemplary embodiment of the present invention.

FIG. 2 is a vertical cross sectional view of the magnetization jig.

FIG. 3 shows a plan view, as seen from the above, of a rotor inaccordance with a first exemplary embodiment of the present invention.

FIG. 4 is a vertical cross sectional view of the rotor.

FIG. 5 is a perspective view used to show a process of how magnets areinserted in accordance with a second exemplary embodiment of the presentinvention.

FIG. 6 is a cross sectional view used to show the magnetization processand measurement process in the second embodiment.

FIG. 7 is a cross sectional view used to show a step of fitting themagnetizing jig in accordance with the second embodiment of the presentinvention.

FIG. 8 is a cross sectional view used to show a step oftransferring/inserting the magnet in the second embodiment.

FIG. 9 is a vertical cross sectional view showing a compressor inaccordance with a third exemplary embodiment of the present invention.

FIG. 10 is a vertical cross sectional view showing a compressor inaccordance with a fourth exemplary embodiment of the present invention.

FIG. 11 shows a vertical cross sectional view of a conventionalcompressor.

FIG. 12 shows a cross sectional view, as viewed from above, of aconventional compressor, with the sealed vessel cut into two pieces.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are described in thefollowing referring to the drawings.

The preferred sorts of magnet for use as the magnet of the presentinvention are those having a large energy product. Specific preferenceis for the rare-earth magnet, such as a samarium-cobalt system magnet ora neodymium system magnet. In the exemplary embodiments of the presentinvention, a neodymium system magnet is used.

The iron core portion is formed by stacking a soft magnetic material. Inthe present embodiments, a silicon steel sheet is used as an example ofthe soft magnetic material.

The drawings have been provided to illustrate the concept of theinvention, they are not intended to give precise dimensions orlocations.

First Exemplary Embodiment

As shown in FIG. 1 through FIG. 4, magnetizing jig 100 has anapproximate cylindrical shape and is made of a stainless steel or anonmagnetic material.

Magnetizing jig 100 is provided at the center with through hole 102 forcoupling with a shaft, and slot 104 to be used for receiving a magnetalong an original direction of the through hole. There are four slots104 around through hole 102.

Respective slots 104 have, at their middle part, hole 106 whose diameteris greater than the width of the slot. Hole 106 is provided for allowinga push-out pin to go through.

Rotor 110 of a dipole magnet type motor includes iron core portion 112formed by stacking silicon steel sheets and die-cast aluminum end-ring114 disposed at both end-faces of iron core portion 112.

At the vicinity of an outer circumference of iron core portion 112, aplurality of die-cast aluminum secondary conductors 115 is providedconnecting end-rings 114 through. Iron core portion 112 is provided atthe center with opening 116 for press fitting with a shaft, and magnetslots 118 for holding the magnet around opening 116. End-ring 114 isformed, at the inner circumference, in an oval shape with both of itsend regions cut off. Provided fixed at the bottom end-face of iron coreportion 112 is end-plate 119 for sealing the open bottom-end of magnetslot 118.

The outside shape of magnetizing jig 100 is regulated by rotor 110'send-ring 114 which has an approximate oval shape with its both endregions cut off. Magnetizing jig 100 is designed so that it fits to theupper end-face of rotor 110.

Magnetizing jig 100's four slots 104 are located so that they coincidewith rotor 110's magnet slots 118, when magnetizing jig 100 is fitted torotor 110.

The above-configured magnetizing jig 100 loaded with magnetized magnetsinserted in the respective slots is fitted onto the upper end-face ofrotor 110. The magnets are pushed out of magnetizing jig 100 to beinserted in magnet slots 118 of rotor 110. The magnets are thustransferred into magnet slots 118.

Since magnetizing jig 100 is made of a stainless steel, or a nonmagneticmaterial, the magnets do not stick to magnetizing jig 100. Therefore,the magnets can be pushed out of magnetizing jig 100 and inserted intorotor 110's magnet slots 118 easily, encountering only a very smallresisting force. In other words, the magnet transferring operation iscarried out smoothly; there is little possibility of causing damage tothe magnets. This is the point of significant importance when handling amagnet of great magnetic force, such as a neodymium magnet.

The magnets stay within magnetizing jig 100 taking advantage of mutualmagnetic force. Therefore, the magnets do not fall down even if slot 104is positioned in parallel with the direction of gravitation. Thus, themagnetizing jig can be handled with ease. The magnets held withinmagnetizing jig 100 are pushed out by a push-out pin inserted in thehole of respective slots 104. In this way, respective magnets aretransferred simultaneously with high reliability into magnet slots 118to be retained therein at their specified locations.

As described above, the present embodiment implements a magnetizing jigthat can be handled with significant ease and high efficiency for theassembly of compressors.

Although magnetizing jig 100 in the present embodiment has been formedof a stainless steel, other nonmagnetic materials such as a nonferroussystem metal or a resin material may of course be used for themagnetizing jig.

Other preferred materials include a nonferrous metal such as an aluminumalloy provided with an improved surface hardness by an Alumite coating,a resin material provided with a self-lubricating property such as byuse of ethylene tetrafluoride, etc.

Second Exemplary Embodiment

The present embodiment describes a method for assembling a rotor andcompressor.

In the first place, a step of inserting magnets into a magnetizing jigis described.

Reference is made to FIG. 5, magnets 130 at a pre-magnetization state(i.e., pre-magnetized magnets) are inserted into the four slots of 104magnetizing jig 100. After being loaded with magnets 130, magnetizingjig 100 is held approximately perpendicular to the direction of gravityso that magnets 130 do not fall down out of slot 104 due to their ownweight. Since magnets 130 at this stage are not yet magnetized, there isno magnetic force working among them. So, the magnets can be insertedeasily into slots 104. The step of insertion is thus easily completed.Next, a step of magnetizing the magnets is described.

Magnetizing coil 140 wound in an approximate cylindrical shape, as shownin FIG. 6, is connected with a power supply source (not shown) capableof delivering a large electric current. The magnetizing coil isaccompanied by search coil 142 wound in an approximate cylindricalshape.

Magnetizing coil 140 and search coil 142 are both immersed in a varnishand fixed.

The magnetizing jig loaded with the pre-magnetization magnets is carriedto the inside of magnetizing coil 140, with slots 104 kept substantiallyperpendicular to the gravitational force direction. The magnetizing jigis held and carried by a dedicated jig (not shown) to a certain specificplace inside magnetizing coil 140.

Then, the above-described power supply source (not shown) delivers acertain specific electric current to magnetizing coil 140 in order tomagnetize magnets 130. This completes the step of magnetization.

The above-described certain specific electric current means an electriccurrent that is sufficient to generate magnetic fields needed formagnetizing the magnets to a certain predetermined level. Search coil142 measures the magnetic flux of magnets 130; so, a possible error inthe magnetization can be prevented.

The step of magnetizing the magnets by supplying electricity to the coilwound around the magnetizing jig and the step of measuring the magneticflux of magnetized magnets are now completed.

Next, a step of fitting the magnetizing jig onto a rotor at the end-faceis described. As shown in FIG. 7, a compressor's mechanical section 190includes motor 205 formed of stator 203 and rotor 110, and compressingelement 210 which is driven by motor 205. Mechanical section 190contains rotary shaft 212, and cylinder 216 which supports shaft 212 andforms compression chamber 214. After shaft 212 and rotor 110 are coupledand fixed together, a spacer of certain specific thickness is placedbetween rotor 110 and stator 203 and then stator 203 is fixed tocylinder 216. The spacer is removed afterwards. In this way, a certainspecific gap 220 is provided between stator 203 and rotor 110. Normally,the certain specific gap is 1 mm or less, and a preferred gap isapproximately 0.5 mm.

Since rotor 110 is not yet loaded with magnets 130 at this stage, therecan be no possibility of dislocation due to magnetic forces of themagnets. Therefore, the dimensional accuracy with gap 220 between stator203 and rotor 110 can be ensured to be substantially homogeneous overthe entire circumference.

On mechanical section 190 thus assembled, magnetizing jig 100 withmagnetized magnets 130 retained therein within is fitted to the upperend-face of rotor 110.

The step of fitting the magnetizing jig on the rotor is thus completed.

Finally, a step of transferring the magnets into the rotor's magnetslots 118 is described. As shown in FIG. 8, rotor 110 and magnetizingjig 100 have been fitted together. Rod-shaped push-out pins 180 disposedat holes 106 are pressed downward by push member 182. Magnets 130 arepushed to be inserted into magnet slots 118 of iron core portion 112.Magnets 130 proceed until they have mechanical contact with end-plate119, and stop there. Thereby, magnets 130 are placed at certain specificlocations. This completes the step of pushing magnetized magnets 130 outof the jig's slots 104 and inserting them into magnet slots 118.

As described above, magnetized magnets can be transferred easily andsmoothly into a rotor in accordance with the present embodiment. Thusthe operation efficiency is high. Furthermore, there is no need toimmerse the stator coil in a varnish, because the coil is not requiredto withstand a large over current. In this way, the present embodimentoffers a method for assembling reliable compressors at low cost.

Third Exemplary Embodiment

With reference to FIG. 9, sealed vessel 200 houses motor 205 havingstator 203 and rotor 110, and compressing element 210 driven by motor205.

Compressing element 210 includes rotary shaft 212, and cylinder 216which supports shaft 212 and forms compression chamber 214. Shaft 212and rotor 110 are coupled and fixed together, and stator 203 is fixed oncylinder 216 so that it is coaxial to shaft 212 and so that there is acertain specific gap 220 between rotor 110 and stator 203.

Rotor 110 includes iron core portion 112 and die-cast aluminum end-ring114 provided at both end-faces of iron core portion 112. At the vicinityof the outer circumference of iron core portion 112, a plurality ofsecondary conductors 115 made of die-cast aluminum is providedconnecting end-rings 114 through. Magnet slots 118 for storing magnetshave been loaded with magnets 130. These constitute a dipole magnet typemotor. Provided fixed at the bottom end-face of iron core portion 112 isend-plate 119 for sealing the open bottom-ends of magnet slots 118. Thetop-ends of magnet slots 118 are left open, with no end-plate attached.The method of assembling the compressor remains the same as that in thesecond embodiment.

Now the operation of the above configuration is described.

When electric power is delivered from a home power source to stator 203,rotor 110 rotates in engagement with shaft 212. Compressing element 210compresses the gas sucked in compression chamber 214.

The compressor has been assembled in accordance with the same method asdescribed in the second embodiment. The assembly operation is easy andthe efficiency is high, and there is no need to deliver an over-currentto the stator. Therefore, the compressors thus assembled exhibit a highreliability.

Furthermore, there is no need to immerse the stator coil in a varnish.This contributes to a reduction in the manufacturing cost.

Still further, since magnets 130 kept at certain specific places inmagnet slots 118 are magnetically sticking (adhering) to the siliconsteel sheets forming the iron core portion, the magnets can hardly bedisplaced away from the certain specific places unless they are affectedby an extraordinary force. Therefore, there is no need seal the openends of magnet slots 118; at least a sealing process at the insertionends (open ends at the top end-face) can be eliminated.

Further, end-plate 119 in the present embodiment can also be eliminated,because magnets 130 are pushed downward, via push member 182, withrod-shaped push-out pins 180 disposed in holes 106 for a certainspecific distance to be inserted into magnet slots 118 of iron coreportion 112 until they reach a certain specific place. This contributesto the implement action of an inexpensive compressor consisting of areduced number of constituent components.

As described above, a reliable compressor consisting of smallercomponent counts can be offered at a low cost in accordance with thepresent embodiment.

Fourth Exemplary Embodiment

Those constituent portions in the present embodiment identical to thoseof the third embodiment are represented by using the same symbols, andfurther detailed description thereof is omitted.

As shown in FIG. 10, sealed vessel 200 houses motor 305 having stator303 and rotor 310, and compressing element 210 driven by motor 305.

Compressing element 210 includes rotary shaft 212, and cylinder 216which supports shaft 212 and forms compression chamber 214.

Shaft 212 and rotor 310 are coupled and fixed together, and stator 303is fixed on cylinder 216 so that it is coaxial to shaft 212 and there isa certain specific gap 320 between stator 303 and rotor 310.

Rotor 310 is provided at iron core portion 312 with magnet slots 318 forholding the magnets, and magnets 330 are kept within magnet slots 318.Thus, an inverter-driven DC motor is structured. Provided fixed at thebottom end-face of iron core portion 312 is end-plate 319 for sealingthe open bottom-end of magnet slots 318. The method of assembling thecompressor remains the same as that in the second embodiment.

Now operation of the above configuration is described.

When electricity is delivered to stator 303 from an inverter circuit(not shown), rotor 310 rotates in engagement with shaft 212.

Compressing element 210 compresses the gas in compression chamber 214.

Since the compressor has been assembled in the same method as in thesecond embodiment, the assembling operation is easy and the efficiencyis high. Furthermore, the stator is not required to withstand a bigcurrent. Therefore, the compressors thus assembled exhibit a highreliability.

Furthermore, there is no need to immerse the stator coil in a varnish.This is a contribution to the reduction of manufacturing cost.

Still further, since magnets 330 kept at the certain specific places inmagnet slots 318 are magnetically sticking (adhering) to the siliconsteel sheets forming the iron core portion, they are hardly displacedfrom their specific places unless they are affected by an extraordinaryforce. Therefore, there is no need to seal open ends of magnet slots118; at least a sealing at the insertion ends (open ends at the topend-face) can be eliminated.

Still further, magnets 330 are pushed downward, via push member 182, fora certain specific distance with rod-shaped push-out pins 180 disposedin holes 106 so that they reach certain specific places in magnet slots318 of iron core portion 312. Therefore, end-plate 319 described in thepresent embodiment can also be eliminated. As the result, an inexpensivecompressor consisting of a reduced number of components is implemented.

As described above, the present embodiment offers at a low manufacturingcost compressors of high reliability assembled with fewer constituentcomponents.

As explained in the foregoing descriptions, the present invention offersthe following advantages.

The magnetizing jig in accordance with the present invention makes iteasy to push the magnetized magnets out of the jig. So, the efficiencyof the assembling operation is improved.

The magnetizing jig offers the same advantage even in a case when a rareearth magnet of strong magnetic force is used.

The magnetizing jig makes it easy to push out the magnetized magnetsfrom the slots and transfer them into a rotor's slots. So, theefficiency of the assembling operation is improved.

The method for assembling a rotor in accordance with the presentinvention magnetizes the magnets without delivering electricity to thestator coil. Thus the present invention offers a method of assemblingthe rotors needed to implement the reliable yet low cost compressors.

The method for assembling a rotor in accordance with the presentinvention makes it possible to deliver only those magnets which havebeen magnetized without fail for the assembly of rotors. Thus thepresent invention offers an assembling method, where the rotors areprovided with only such magnets that have been surely magnetized.

The relative positioning between stator and rotor has been fixed keepinga certain specific gap among them. The certain specific gap can not beill-affected by the influence of magnetic forces. Therefore, theassembling method provides compressors having a high reliability.

A compressor in the present invention uses a dipole permanent magnettype motor, which includes a secondary conductor provided at thecircumference region of the rotor's iron core portion and the magnetsbuilt in the rotor's iron core portion. The compressors employing thedipole permanent magnet type motor can be assembled easily with highreliability in accordance with the present invention.

Furthermore, compressors employing an inverter-driven DC motor can beassembled easily and with high reliability in accordance with thepresent invention.

Since the magnetized magnets stay within the magnet slots takingadvantage of the self magnetic forces, a member for sealing the slotsbecomes unnecessary. So, the compressors having fewer components can beoffered at a low manufacturing cost in accordance with the presentinvention.

A reliable and inexpensive dipole permanent magnet type motor consistingof fewer components and requiring fewer assembly steps can be providedin accordance with the present invention.

A compressor employing an inverter-driven DC motor consisting of fewercomponents counts and requiring fewer assembly steps can be provided, inaccordance with the present invention.

INDUSTRIAL APPLICABILITY

The present invention offers such electric compressors having fewercomponents counts that can be assembled through easy assembly steps, yetprovide a high reliability.

1. An electric compressor comprising: a sealed vessel; a motor having astator and a rotor rotatable relative to said stator; and a compressingelement operably coupled to said motor to be driven by said motor;wherein said motor and said compressing element are housed in saidsealed vessel; wherein said rotor includes an iron core portion having aplurality of magnet slots penetrating therethrough; wherein a pluralityof magnets are disposed in said magnet slots of said iron core portionof said rotor; and wherein said magnets adhere, inside said magnetslots, to said rotor core portion via only magnetic force.
 2. Theelectric compressor according to claim 1, wherein said magnet slots arekept open.
 3. The electric compressor according to claim 1, wherein eachof said magnet slots has slot end openings at opposing ends thereofopening at axially opposing ends of said rotor core portion; and foreach of said magnet slots, both of said opposing ends are kept open. 4.The electric compressor according to claim 1, wherein said magnets areconstituted by rare earth magnets.
 5. The electric compressor accordingto claim 1, wherein said motor is a dipole permanent magnet type motor,said rotor including a secondary conductor provided circumferentiallyabout said iron core portion and said magnets disposed in said iron coreportion.
 6. The electric compressor according to claim 1, wherein saidmotor comprises an inverter-driven DC motor.